KR20080077935A - Homogeneous charge compression ignition engine and air intake and exhaust system thereof - Google Patents

Abstract

A homogeneous charge compression ignition engine and devices for air intake and exhaust gas are provided to cool the re-circulated exhaust gas, and to heat intake air while saving space occupied by the devices. An engine(1) having homogeneous charge compression ignition system includes a combustion chamber(10), an air intake passageway(11p) leading to the combustion chamber, and an exhaust gas passageway(12p) extended fro the combustion chamber. The homogeneous charge compression ignition system has a turbo charger(11t), a throttle(3), a fuel valve(2v), a passageway(20p) to preheat the intake air, a switch valve(11v), an EGR(Exhaust Gas Recirculation) passageway(30p), an EGR valve(30v), a heat exchanger(40), an intake valve(51v), an exhaust valve(52v), a spark plug(53c), an ECU(Electronic Control Unit,5) where control cables(5a~5i) for various devices are connected to control operation of the connected devices such as the exhaust valve, the spark plug, the intake valve, the EGR valve, the switch valve, the throttle, the fuel valve, the by-pass control valve, and the turbo charger.

Description

Premixed compression ignition engine and its intake and exhaust devices {HOMOGENEOUS CHARGE COMPRESSION IGNITION ENGINE AND AIR INTAKE AND EXHAUST SYSTEM THEREOF}

The present invention relates to a premixed compression ignition engine and an intake and exhaust device thereof for returning exhaust gas as an EGR gas to a combustion chamber.

In recent years, in the field of an internal combustion engine, the premixed compression ignition engine which obtains favorable fuel efficiency and thermal efficiency is attracting attention, and various research is performed. Most premixed compression ignition engines are configured to mix fuel and air on an intake passage and to supply the resulting mixer to the combustion chamber. Then, the mixer trapped in the combustion chamber is self-ignited in response to the high temperature and high pressure caused by the piston rising during the compression stroke. In such a premixed compression ignition engine, as one of the problems for practical use, it is known that the operation region which can stably control premixed compression ignition combustion (HCCI) is still narrow. Therefore, for the purpose of avoiding this problem, first, in order to put the premixed compression ignition engine into practical use in a stationary engine having a relatively narrow operating area, for example, a gas engine for GHP (gas heat pump), etc. There is a movement. In addition, premixed compression ignition combustion is performed in the vicinity of the low-speed rotation and low-load load areas, which are frequently used in actual operation, and suitable operation is performed to perform spark ignition combustion (SI) in the high-rotation area and the extremely low and high load areas. Switching is also proposed.

In the premixed compression ignition engine, the operation region capable of stably controlling the premixed compression ignition combustion is narrow. This problem will be described in detail below. For example, in the low load operation region, the amount of the mixer supplied in the combustion chamber is small, and the internal temperature of the cylinder is also less likely to rise, so that ignition deteriorates and misfire is likely to occur. In order to suppress the occurrence of such misfire, a negative overlap period is added to the valve timing of the intake valve and the exhaust valve so that a part of the existing combustion gas is left in the combustion chamber so that it can be transferred to the next combustion. It is known to use so-called internal EGR to set. By using the internal EGR in this manner, the high temperature internal EGR gas and the mixer newly supplied into the combustion chamber are mixed to raise the cylinder temperature, so that the ignition in the premixed compression ignition combustion is improved and misfire is suppressed. However, if the conditions deteriorate further at low outside air temperature or the like, the combustion chamber temperature is low and high temperature internal EGR is difficult to be obtained. Therefore, even if the internal EGR is used, premixed compression ignition is unlikely to occur, causing misfire. It may occur.

In addition to the internal EGR, as a means for raising the cylinder temperature in the combustion chamber, for example, in a diesel engine, intake (mixer) heated in advance in a heating mechanism such as a heat exchanger is introduced into the combustion chamber, that is, intake heating is generated. Means for preventing this are known.

On the other hand, in the premixed compression ignition engine, abnormal combustion such as knocking and premature ignition occurs in the high load operating region. In order to suppress occurrence of such abnormal combustion, it is known to use external EGR (Exhaust Gas Recirculation). Since the external EGR gas immediately after being taken out from the exhaust passage is high temperature, it is cooled by the EGR cooler formed in the middle of the EGR passage so as not to deteriorate the volume efficiency of the intake air. Then, the EGR gas cooled by the EGR cooler is refluxed in the combustion chamber, whereby the combustion state of the combustion chamber is relaxed by the increase of the inert gas.

As an example of a heat exchanger as a heating device or a heat exchanger as an EGR cooler, Japanese Patent Laid-Open No. 2005-517857 in Patent Document 1 uses a heat exchanger 12 to perform heating of intake air and cooling of an external EGR gas. The technique is disclosed (refer FIG. 2 of patent document 1). In this technique, the heat exchange mechanism is relatively simplified by cooling the EGR gas and intake heating using the same cooling water.

However, although the heat exchanger of the said patent document 1 has one casing, it has a separate 1st heat exchange part and a 2nd heat exchange part inside, and each heat exchange part performs cooling of the EGR gas and intake heating in a different system. It is structured. For this reason, although the heat exchanger of patent document 1 can save space compared with two conventional heat exchangers, it becomes larger than the general heat exchanger which has only one heat exchange part. Moreover, in the internal combustion engine using the heat exchanger of patent document 1, it is necessary to connect many piping to one heat exchanger including the piping which forms an intake passage, an EGR passage | channel, and the cooling water piping, and arrange | positions around an internal combustion engine Design constraints become strict.

Accordingly, an object of the present invention is to provide a premixed compression ignition engine and an intake / exhaust device of the same, which can further reduce space and perform cooling and intake heating of EGR gas.

In order to achieve the above object, the premixed compression ignition engine of the present invention includes a combustion chamber, an intake passage serving as an intake passage for the combustion chamber, an exhaust passage serving as an exhaust passage from the combustion chamber, the exhaust passage, and the An EGR passage communicating with an intake passage and for recirculating a part of the exhaust gas from the combustion chamber to the EGR gas and returning to the combustion chamber, a heat exchanger formed in the middle of the EGR passage, and a heat exchanger for cooling the EGR gas; Branched from an EGR valve for adjusting the open / closed state of the EGR passage, and a branch formed in an upstream side of the inlet passage from a downstream end of the EGR passage, and a downstream end of the EGR passage in the EGR passage. A heating intake passage communicating with an upstream side of the heat exchanger, the intake passage downstream of the branch and the heating A switching valve for adjusting the amount of intake air passing through each of the intake passages, and the intake air flowing into the combustion chamber when the EGR valve is closed, the intake passage and the heating intake passage downstream of the branch portion. The switching valve is switched so as to pass through at least one of the controls, and when the EGR valve is open, the intake air flowing into the combustion chamber is controlled to switch the switching valve so as to pass only the intake passage downstream of the branch part. It has a control means.

Moreover, in order to achieve the said objective, the intake / exhaust apparatus of the premixed compression ignition engine of this invention is used for the premixed compression ignition engine which has a combustion chamber and the exhaust passage used as the passage of the exhaust from this combustion chamber. And an intake passage leading to the combustion chamber, the exhaust passage and the intake passage, an EGR passage for returning the exhaust gas from the combustion chamber as the EGR gas to the combustion chamber, and formed in the middle of the EGR passage. Branched from a heat exchanger for cooling, an EGR valve for opening and closing the EGR passage, and a branching portion formed upstream from a downstream end of the EGR passage in the intake passage; The amount of intake air passing through each of the intake passages for heating communicated with the upstream side of the heat exchanger in the EGR passage, and the intake passages and the intake passages for heating downstream on the downstream side of the branch portion. A switching valve for adjustment and an intake air flowing into the combustion chamber when the EGR valve is closed The switching valve is switched so as to pass through at least one of the intake passage and the heating intake passage, and when the EGR valve is open, the intake air flowing into the combustion chamber is downstream of the branch. And control means for controlling the switching valve to pass through only the passage.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described, referring drawings.

(Overall configuration)

With reference to FIG. 1, the whole structure of the premixed compression ignition engine and the intake / exhaust apparatus which concern on one Embodiment of this invention is demonstrated. In the following description, "intake" means a gas (for example, a mixture of intake air and a gas fuel, a mixture of intake air, gas fuel, and external EGR gas, etc.) supplied to a combustion chamber, and a "mixer". "Shall mean that the intake air and gaseous fuel are mixed.

As shown in FIG. 1, the premixed compression ignition engine 1 includes a combustion chamber 10, an intake passage 11p leading to the combustion chamber 10, and an exhaust passage 12p serving as a passage of the exhaust gas from the combustion chamber 10. In accordance with the operating conditions (load and engine speed), the operation is performed by appropriately switching the spark ignition combustion and the premixed compression ignition combustion. In this way, by switching the premixed compression ignition combustion and the spark ignition combustion in accordance with the operating conditions, both low fuel consumption due to the premixed compression ignition combustion and good startability and high output due to the spark ignition combustion can be achieved.

In addition, the premixed compression ignition engine 1 includes a supercharger 11t, a throttle 3, a fuel valve 2v (fuel supply amount adjusting means), a heating intake passage 20p, a switching valve 11v, an EGR passage ( 30p), the EGR valve 30v, the heat exchanger 40, the intake valve 51v, the exhaust valve 52v, and the spark plug 53c (these details are mentioned later). In addition, the premixed compression ignition engine 1 has an ECU 5 (equivalent to an electronic control unit). The ECU 5 includes an exhaust valve 52v, a spark plug 53c, an intake valve 51v, an EGR valve 30v, a switching valve 11v, a throttle 3, a fuel valve 2v, a bypass control valve. 40v and control cables 5a-5i corresponding to the supercharger 11t are electrically connected. And ECU 5 is exhaust valve 52v, spark plug 53c, intake valve 51v, EGR valve 30v, switching valve 11v, throttle 3, fuel valve 2v, bypass It is comprised so that operation of the control valve 40v and the supercharger 11t may be controlled.

(About an intake apparatus)

The intake and exhaust device 60 of the premixed compression ignition engine 1 according to the present embodiment is used for supplying intake air to the combustion chamber 10, scavenging exhaust gas from the combustion chamber 10, and the like. ), Exhaust passage 12p, heating intake passage 20p, switching valve 11v, EGR passage 30p, EGR valve 30v, heat exchanger 40, and ECU 5. In addition to the intake air supply and the like described above, the intake and exhaust device 60 performs mixing of the external EGR and the mixer, intake heating, and the like.

(mixer)

The premixed compression ignition engine 1 has a mixer 4 in the middle of an intake passage 11p, and the mixer 4 is supplied with gas fuel through a fuel supply passage 2p communicating with the mixer 4 ( That is, the fuel supply passage 2p serves as a passage of the gaseous fuel and communicates with the intake passage 11p). Then, air and fuel are mixed in the mixer 4.

(Fuel valve)

The fuel valve 2v is formed in the middle of the fuel supply path 2p. And the ECU 5 controls the fuel valve 2v, and the opening degree of the fuel valve 2v is adjusted, thereby adjusting the supply amount of the gaseous fuel supplied to the intake passage 11p.

(Throttle)

As shown in FIG. 1, the throttle 3 is comprised with the shaft 3c and the step motor (not shown) which drives the valve part 3v, and the valve part 3v is centered around the axis 3c. It is rotatable. Then, the ECU 5 controls the step motor of the throttle 3, whereby the opening degree of the passage is adjusted by the valve portion 3v, whereby the amount of intake air supplied to the combustion chamber 10 through the intake passage 11p. This is adjusted.

(supercharger)

The supercharger 11t is an electric turbo type with a variable boost pressure and is configured as a centrifugal compressor driven by the electric motor M. As shown in FIG. The supercharger 11t is disposed in the middle of the intake passage 11p. In addition, the bypass path 40a and the main path 40b are connected to each of the upstream side of the supercharger 11t and the outlet of the supercharger 11t, and the intake passage 11p is communicated through them. In the middle of the bypass path 40a, a bypass control valve 40v for opening and closing the bypass path 40a is formed.

When the supercharger 11t is not used, the electric motor M is stopped controlled, and the bypass control valve 40v is opened controlled. Thereby, the bypass path 40a functions as a normal intake passage. On the other hand, when supercharging is performed using the supercharger 11t, while the electric motor M is rotationally driven-controlled, the bypass control valve 40v is cut-off-controlled. As a result, the main path 40b functions as a supercharged passage.

(combustion chamber)

The combustion chamber 10 is an internal space formed by a cylinder and a piston in an internal combustion engine, and the piston 50 reciprocates in the vertical direction in the figure. The mixer is supplied to the combustion chamber 10 through the intake passage 11p. After the combustion, the exhaust gas is discharged through the exhaust passage 12p. An intake valve 51v and an exhaust valve 52v are disposed in the opening to the combustion chamber 10 of the intake passage 11p and the opening to the combustion chamber 10 of the exhaust passage 12p, respectively. Intake and exhaust are performed by appropriately opening and closing control in accordance with the rise and fall of the piston 50 in each stroke of compression, combustion, expansion, and exhaust. More specifically, the intake valve 51v and the exhaust valve 52v are opened and closed by cams 51c and 52c formed on the outer periphery of the camshaft (not shown), respectively, and by a known variable valve timing mechanism formed on the camshaft. , The opening and closing timing (phase for crank angle) is changed. The spark plug 53c is used for ignition during spark ignition combustion, and its operation is controlled by the ECU 5.

(EGR passage)

The exhaust from the combustion chamber 10 is discharged to the outside from an exhaust port not shown through the exhaust passage 12p, and a part of the exhaust discharged to the exhaust passage 12p is supplied to the combustion chamber 10 again. The EGR passage 30p is for refluxing a part of the exhaust gas from the combustion chamber 10 to the combustion chamber 10 as the EGR gas. The EGR passage 30p branches off from the exhaust passage 12p at the branch position 12b and further downstream thereof. 30b is formed to communicate with the intake passage 11p. As a result, the internal space of the exhaust passage 12p and the intake passage 11p and the internal space of the EGR passage 30p are located upstream of the EGR passage 30p (branch position 12b) and the downstream end 30b. It is in communication.

During the EGR passage 30p, the EGR valve 30v for adjusting the opening / closing state of the EGR passage 30p and the heat exchanger 40 for cooling the EGR gas are upstream (with respect to the direction in which the EGR gas flows). Are formed in this order. Moreover, as mentioned later, the communication part 20b is arrange | positioned between the EGR valve 30v and the heat exchanger 40 in the EGR passage 30p, and the downstream end of the heating intake passage 20p is connected. .

(heat transmitter)

The heat exchanger 40 is formed in the middle of the EGR passage 30p and functions as a cooling device for the EGR gas. The heat exchanger 40 also functions as an intake air heating device when the switching valve 11v is switched so that the intake passage (mixer) passes through the heating intake passage 20p.

In addition, the heat exchange medium of the heat exchanger 40 is a circulating coolant of an engine, and the heat exchanger 40 functions as a heat exchanger by passing this inside this circulating coolant (refer to arrow A, A 'of FIG. 1). At the time of engine operation, the circulating cooling water which cooled a cylinder block and became high temperature is circulated from an engine to an external radiator, and is cooled by a radiator, and the cooling water temperature is maintained at about 70-80 degree | times.

(Heating intake passage)

The heating intake passage 20p becomes a part of the intake passage when intake heating is performed. In the intake passage 11p, the heating intake passage 20p is disposed in the intake flow passage 11p than the downstream end 30b of the EGR passage 30p. Branch) from the branched portion 11b formed on the upstream side. In addition, the downstream end of the heating intake passage 20p is the upstream side of the heat exchanger 40 in the EGR passage 30p in the communication section 20b (upstream side with respect to the direction in which the EGR gas flows). It is formed to communicate with.

(Switching valve)

The switching valve 11v measures the amount of intake (mixer) passing through each of the intake passage 11p and the heating intake passage 20p on the downstream side (with respect to the flow direction of the intake) than the branch portion 11b. It is to adjust. The mixer sent from the upstream to the branching part 11b passes through the branching part 11b by adjustment of the switching valve 11v, and is then heated at the intake passage 11p and downstream of the branching part 11b. It is determined by what ratio the two circulation passages of the intake passage 20p are distributed. Specifically, (a) a path in which all the mixers pass through the intake passage 11p as it flows into the combustion chamber 10 (intake passage: 100%) on the downstream side of the branch portion 11b (b), the branch portion (b) On the downstream side (11b), all the mixers pass through the heating intake passage 20p, pass through a part of the EGR passage 30p, and again pass through the intake passage 11p and flow into the combustion chamber 10. Passage (heating intake passage: 100%), and (c) the path in their intermediate state (downstream from the branch portion 11b, some mixers pass through the intake passage 11p, and some mixers The path through the heating intake passage 20p).

Specifically, the switching valve 11v has a valve for intake passage 11p (not shown) and a valve for heating intake passage 20p (not shown). 11b) It is comprised so that the passage air intake amount of each of the intake passage 11p and heating intake passage 20p in a downstream side may be adjusted. In this embodiment, although the switching valve is comprised in this way, it is not limited to the thing of such a form.

(ECU)

The ECU 5 controls the switching valve 11v as follows. First, when the EGR valve 30v is closed, the mixer which flows into the combustion chamber 10 is an intake passage 11p and a heating intake passage 11 on the downstream side (with respect to the intake flow direction) of the branch portion 11b. The switching valve 11v is switched to pass through at least one of 20p). On the other hand, when the EGR valve 30v is open, the mixer flowing into the combustion chamber 10 passes only the intake passage 11p on the downstream side of the branch portion 11b (the mixer is a heating intake passage 20p). Instead of passing through, the switching valve 11v is switched so that all the mixers pass through the intake passage 11p.

(About exhaust and external EGR)

Next, the exhaust and the external EGR will be described. At the time of premixed compression ignition combustion, abnormal combustion states are likely to occur in the operating region on the high load side. Thus, in the premixed compression ignition engine 1, the EGR gas is cooled in the heat exchanger 40 formed in the middle of the EGR passage 30p by opening the EGR valve 30v in the operation region on the high load side. It feeds into the combustion chamber 10 together. As a result, the combustion state of the combustion chamber 10 is relaxed.

(About internal EGR)

Next, the internal EGR will be described. The premixed compression ignition engine 1 has a negative overlap period in the valve timing at the time of premixed compression ignition combustion operation, and performs premixed compression ignition combustion using the internal EGR. Here, the negative overlap period is a period in which both the exhaust valve 52v and the intake valve 51v are closed in the vicinity of exhaust top dead center, and the exhaust valve 52v is closed before reaching the exhaust top dead center. Thereby, a part of gaseous combustion gas (internal EGR gas) can remain in the combustion chamber 10, and can be transferred to next combustion. By setting the negative overlap period and using the internal EGR, since the high temperature internal EGR gas is mixed with the mixer newly supplied into the combustion chamber 10 to raise the cylinder temperature, the ignition at the time of premixed compression ignition combustion is improved. . Then, by controlling the length of the negative overlap period, the ignition timing can be controlled to some extent.

(About supercharge and external EGR)

Next, supercharging and external EGR will be described. In the case of high load operation, since the supply amount of the mixer containing gaseous fuel increases, the ignition property is excessively improved, and knocking due to too intense combustion is likely to occur. In order to suppress the occurrence of knocking, it is necessary to reduce the amount of internal EGR in the combustion chamber 10 for the purpose of lowering the flammability. Therefore, the control which narrows a negative overlap period is implemented. However, since the reduction of the internal EGR simultaneously causes the perception of the ignition timing and the decrease in the combustion speed, the ignition timing and the combustion speed cannot be controlled in an appropriate balance in that state. Therefore, first, the ignition timing is controlled by maintaining the appropriate timing by raising the intake air temperature by supercharging. In addition, when the operating region of the engine is on the high load side, external EGR is performed to suppress abnormal combustion to slow the combustion speed.

(action)

Next, operation | movement of the premixed compression ignition engine 1 comprised as mentioned above is demonstrated. First, in the operation region where spark ignition combustion is performed, the ECU 5 controls the spark plug 53c or the like, whereby spark ignition combustion is performed.

On the other hand, in the operation region where premixed compression ignition is performed, the ECU 5 performs the following control. First, the mixer produced by the mixer 4 reaches the position of the branch part 11b in which the switching valve 11v is arrange | positioned through the intake passage 11p, adjusting the intake amount by the throttle 3.

And when the EGR valve 30v is closed, the mixer which flows in into the combustion chamber 10 will take in at least one of the intake passage 11p and the heating intake passage 20p in the downstream of the branch part 11b. To pass, the switching valve 11v is switched. Here, since the mixer passes through the heat exchanger 40 when the mixer passes through the heating intake passage 20p, the mixer is heated in the heat exchanger 40. Therefore, the mixer of the outside air temperature passes through the heating intake passage 20p, and is supplied to the combustion chamber 10 in the state where the water temperature of several dozen degrees is previously raised. At low ambient temperature or the like, since the temperature inside the combustion chamber is low or a high internal EGR is hard to be obtained, premixed compression ignition is unlikely to occur, and if premixed compression ignition combustion is performed, there is a risk of misfire. However, by introducing the intake air (mixer) previously heated in this way into the combustion chamber 10, the operation area | region which can perform premixed compression ignition combustion by suppressing generation of misfire can be expanded.

The case where the EGR valve 30v is closed corresponds to the case where the EGR valve 30v is in an operating region in which no external EGR needs to be used. As shown in FIG. 3, in the operation region determined according to the engine load and the engine speed, the premixed compression ignition combustion region (the operating region suitable for premixed compression ignition combustion) corresponds to the center portion of the figure. Of these premixed compression ignition combustion regions (a, b, c, d regions), a, b and c regions become operating regions that do not use external EGR.

On the other hand, when the EGR valve 30v is open, the switching valve 11v is switched so that the mixer flowing into the combustion chamber 10 passes only the intake passage 11p on the downstream side of the branch portion 11b. In other words, when the EGR valve 30v is open, the switching valve 11v is controlled so that the mixer does not pass through the heating intake passage 20p.

And since the EGR valve 30v is open, a part of exhaust gas from the combustion chamber flows in the EGR passage 30p, is cooled by the heat exchanger 40, and is downstream of the downstream end 30b which communicates with the intake passage 11p. ) Flows into the intake passage 11p and is refluxed to the combustion chamber 10 (that is, both the mixer and the external EGR gas are sent to the combustion chamber 10). In this way, when the EGR valve 30v is in the valve open state, the heat exchanger 40 functions as a cooling device in the external EGR.

In the high load operation region, abnormal combustion such as knocking or premature ignition occurs, and by using the external EGR in this way, occurrence of abnormal combustion can be suppressed. More specifically, the external EGR gas is at a high temperature (for example, about 300 degrees before the heat exchanger) and is cooled in the heat exchanger (EGR cooler) 40 formed during the EGR passage 30p. As the cooled EGR gas is refluxed in the combustion chamber 10, the combustion state of the combustion chamber 10 is relaxed by the increase of the inert gas, and the occurrence of abnormal combustion in the combustion chamber 10 is suppressed.

In addition, the case where the EGR valve 30v is open corresponds to the case where it is in the operation area | region which needs to use external EGR. In the operation | movement area | region determined according to the engine load and engine speed shown in FIG. 3, d area | region of a premixed compression ignition combustion area | region (a-d area | region) becomes an operation area using external EGR. Specifically, in the high load operating region, external EGR is used in conjunction with the supercharging of the mixer. As a result, the intake air temperature rise due to supercharging and the local temperature drop due to external EGR can ensure both flammability and smoothing of the combustion state, and consequently, premixed compression ignition in the region of the high load side. The area that can be burned can be widened.

(Control example of premixed compression ignition engine and intake and exhaust device)

Next, the control example of the premixed compression ignition engine 1 and the intake / exhaust apparatus 60 is demonstrated, referring FIG. 2 is a chart showing the opening and closing and switching control of the EGR valve 30v and the switching valve 11v of the premixed compression ignition engine 1. 2 represents the magnitude of the engine load. The upper chart of FIG. 2 shows the opening degree of the EGR valve. In this chart, the bottom (refer to (i) of FIG. 2) is the state in which the EGR valve 30v is closed, and the opening degree of the EGR valve 30v becomes larger as it goes upwards (refer to (ii) of FIG. 2). . In addition, the lower chart of FIG. 2 has shown the switching state of the switching valve 11v. In this chart, the uppermost position (refer to (1) in FIG. 2) indicates a state in which all of the mixers pass through the heating intake passage 20p on the downstream side of the branch portion 11b. The following position (refer FIG. 2 (3)) has shown the state where all the mixers pass the intake passage 11p in the downstream of the branch part 11b. Moreover, the intermediate position (refer to (2) of FIG. 2) is in the intermediate state thereof, that is, downstream of the branch portion 11b, some of the mixers pass through the intake passage 11p, and some of the mixers The state which passes the heating intake passage 20p is shown.

In addition, as shown in FIG. 2, in the premixed compression ignition engine 1, according to the engine load, it is divided into operation areas, such as NA (natural intake) area | region, a supercharge area | region, and a supercharge / external EGR area | region, and each load Operation control according to the area is performed. In addition, about the range of the horizontal axis of FIG. 2, it shows as a part of full range, and there exists also the area of low load and the area of high load rather than the range shown in the figure.

As shown in FIG. 2, in the NA region and the supercharge region, the EGR valve 30v is closed, and the heating intake passage 20p and the intake passage 11p are used as the intake air. That is, no external EGR is used, and the heat exchanger 40 is used only for intake heating.

On the other hand, in the supercharge / external EGR region, the EGR valve 30v is opened, and the heating intake passage 20p is not used at all. That is, the external EGR is used, and the heat exchanger 40 is used only for cooling the external EGR gas as the EGR cooler.

2 shows an example, and the control of the EGR valve 30v and the switching valve 11v is not limited to such a thing.

(effect)

Hereinafter, the effect by this invention is demonstrated, compared with a diesel engine. In a diesel engine, intake heating is performed in order to suppress generation of unburned fuel components and white smoke during low load operation such as when starting an engine. In addition, by using the external EGR, exhaust gas, which is an inert gas, is supplied to the combustion chamber, and the maximum combustion temperature is lowered to reduce the amount of nitrogen oxides generated. In addition, since a diesel engine injects fuel directly into a combustion chamber, generation | occurrence | production of fuel in a combustion chamber is not avoided, and local hot parts generate | occur | produce, thereby causing a large amount of nitrogen oxides. That is, in diesel engines, the external EGR is used for the purpose of suppressing nitrogen oxides, and in recent years, in which the exhaust gas countermeasure is important, in the low load operation region, the operation region used in combination with intake heating has been expanded.

On the other hand, in the premixed compression ignition combustion, the intake (mixer) is heated during low load operation such as at low outside air temperature and during heavy load operation to improve the ignition and suppress the occurrence of misfire. In addition, in premixed compression ignition combustion, the use of external EGR during high load operation is effective because knocking can be suppressed. However, the use of the external EGR is not preferable in low load operation such as at low ambient temperature and during heavy load operation, because it lowers the flammability. That is, in premixed compression ignition, intake heating improves the flammability and external EGR suppresses the flammability. Therefore, the external EGR and the intake heating are not used in combination because the operating regions used are different.

In addition, in premixed compression ignition combustion, a mixer in which the fuel and air are mixed almost uniformly is magnetized in the combustion chamber, so that a diesel engine in which the fuel is localized, and a flame ignition combustion in which a local high temperature portion is generated in flames (for example, Compared with gasoline engines, local hot spots are less likely to occur and the maximum combustion temperature is also lower. Therefore, the amount of nitrogen oxides generated is small, and there is no need to use external EGR for the purpose of suppressing the generation of nitrogen oxides.

As described above, since the premixed compression ignition engine 1 does not use the external EGR together with intake heating, the heat exchanger 40 generates the EGR gas according to the operating region (determined according to the engine load and the engine speed). Only one of cooling and intake heating is performed. Therefore, since the premixed compression ignition engine 1 is comprised as mentioned above, since the heat exchanger 40 used as an EGR cooler can be used also for intake heating by the structure as it is, the general heat exchanger which has only one heat exchange part. The heat exchanger does not become larger than one. Therefore, cooling and intake air heating of EGR gas can be performed with a simple structure. In addition, by using an existing EGR passage having an EGR cooler, the above configuration can be realized by a simple change and addition of the piping structure. In addition, it is not necessary to connect a plurality of pipes to one heat exchanger, including the pipes constituting the intake passage and the EGR passage and the cooling water pipe, and design constraints for disposing around the internal combustion engine are alleviated, thereby further saving space. In addition, the cooling and intake air heating of the EGR gas can be performed.

In addition, since the EGR valve 30v is formed in the EGR passage 30p on the upstream side of the downstream end of the heating intake passage 20p (communication portion 20b), the heated intake (mixer), In the EGR passage 30p, the gas is refluxed to the combustion chamber 10 via the intake passage 11p and the downstream side than the communication portion 20b of the EGR passage 30p without being flowed upstream from the communication portion 20b. When the EGR valve is closed, the EGR gas can be prevented from flowing into the heating intake passage 20p.

Moreover, since the switching valve 11v is formed in the branch part 11b, it becomes possible to actively send intake | air-intake (mixer) heated by the heat exchanger 40 to the heating intake passage 20p. On the other hand, the intake air (mixer) which does not pass through the heat exchanger 40 does not enter the heating intake passage 20p, and all pass through the intake passage 11p. Therefore, circulation of intake air is performed efficiently.

In addition, since the heat exchanger 40 passes through the circulating cooling water of the engine, the heat of the engine can be used, and the cooling and intake heating of the EGR gas can be performed by a simpler configuration.

Moreover, since the intake / exhaust apparatus 60 of the premixed compression ignition engine of this invention is comprised as mentioned above, cooling and intake heating of EGR gas can be performed by a simple structure. In addition, by using an existing EGR passage having an EGR cooler, the above configuration can be realized by a simple change and addition of the piping structure.

(About expansion of driving possibility range)

In addition, by using the premixed compression ignition engine 1 and the intake and exhaust device 60, the operable range can be expanded to the low load side. This will be described with reference to FIG. 3. 3 is a schematic diagram showing an operating region in the case where the premixed compression ignition engine 1 is used, the horizontal axis represents the engine speed, and the vertical axis represents the engine load.

In FIG. 3, the center part shown as HCCI is an area | region where premixed compression ignition combustion is performed, and other peripheral parts become SI (flame ignition combustion) area | region. In this way, the premixed compression ignition fuel and the spark ignition combustion are appropriately switched and operated according to the engine load and the engine speed.

And when the engine which does not perform intake heating is considered, it is only b area | region of FIG. 3 that operation | movement is performed by natural intake. That is, when intake heating is not performed, operation a is carried out in the region a in the figure by spark ignition combustion. However, when intake heating is performed like the premixed compression ignition engine 1, in addition to the b region, the premixed compression ignition combustion can be operated in the a region.

Hereinafter, it demonstrates more concretely. First, the premixed compression ignition combustion in a region, which is a low load region, is likely to cause misfire because the amount of fuel supplied is small. However, ignitability is achieved by performing intake heating in the a region, that is, closing the EGR valve 30v and switching the intake passage 20p for heating in the switching valve 11v so that the intake (mixer) passes. Since it can improve and suppress generation | occurrence | production of a misfire, premixed compression ignition combustion becomes possible. Thereby, a driveable area | region can be expanded to a low load side.

By performing the above control in the premixed compression ignition engine 1, it becomes possible to expand an operation | movement range to the low load side (region a). In addition, by adjusting the switching valve 11v appropriately, the intake temperature flowing into the combustion chamber 10 is controlled by controlling the distribution amount of the intake air to each of the intake passage 11p and the heating intake passage 20p in accordance with the outside air temperature. Can be adjusted. Therefore, the operating range can be extended to the low load side by adjusting the distribution of intake air regardless of the elevation of the outside air temperature. In addition, the region c in the figure is operated by supercharging, and the region d in the figure can be operated by using the supercharging and the external EGR.

(Variation)

Next, the modification of the premixed compression ignition engine which concerns on the said embodiment is demonstrated centering on a part different from the said embodiment, referring FIG. 4,5. 4 shows an overall schematic diagram of a premixed compression ignition engine according to a first modification, and FIG. 5 shows an overall schematic diagram of a premixed compression ignition engine according to a second modification. In addition, about the part same as the said embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

(First modification)

First, the first modification will be described. In the premixed compression ignition engine 100 and the intake and exhaust device 160 according to the present modification, as shown in FIG. 4, the switching valve 111v and the EGR valve 130v include the heating intake passage 20p and the EGR passage. It is formed in the communication part 20b of 130p. Specifically, the switching valve 111v which is an opening / closing valve is formed in the connection portion of the heating intake passage 20p and the EGR passage 130p, and the EGR serving as the opening / closing valve is located upstream of the communication section 20b in the EGR passage. The valve 130v is formed. Here, the control cable 105d (105e) which connects the switching valve 111v and the EGR valve 130v, and the ECU 105, combined the control cables 5d and 5e in the said embodiment into one. It corresponds to thing. According to this modification, since a switching valve and an EGR valve need only be arrange | positioned as one valve 100v, a premixed compression ignition engine and an intake / exhaust apparatus can be made simple.

(Second modification)

First, the second modification will be described. In the premixed compression ignition engine 200 and the intake and exhaust device 260 according to the present modification, as shown in FIG. 5, the EGR valve 230v communicates with the heating intake passage 20p and the EGR passage 230p. In the vicinity of the portion 20b (downstream end of the heating intake passage), the EGR passage 230p is provided on the upstream side with respect to the flow direction of the EGR. By setting it as such a structure, the effect similar to the said embodiment is acquired.

As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can variously change and implement within the range described in a claim.

For example, in the said embodiment, although the fuel supply path 2p is arrange | positioned so that it may communicate with the upstream side of the branch part 11b in the intake passage 11p, it is not limited to such a position. For example, it may be connected to the downstream side of the connection part (downstream end 30b) with the EGR passage 30p in the intake passage 11p (refer to the arrow C position in FIG. 1). Even if either of the intake passage 11p and the heating intake passage 20p is selected by the switching valve 11v by arrange | positioning the fuel supply path 2p in the arrangement | positioning of the said embodiment, or the arrow C position, suction Fuel can be supplied along the air path. On the other hand, arranging the fuel supply path at a position (see arrow B position in FIG. 1) between the branch portion 11b and the connecting portion (downstream end 30b) in the intake passage 11p is a heating intake passage ( When 20p) is selected, since the communication position to the fuel supply path is not in the middle of the path of the intake air, the supply of fuel is incomplete, which is not preferable.

In addition, in the said embodiment, although the throttle 3 is arrange | positioned in the upstream side of the branch part 11b in the intake passage 11p, it is not limited to such arrangement, but is the connection part (downstream) with EGR passage 30p. It may be provided downstream of the stage 30b (see arrow C position in the drawing). By arrange | positioning the throttle 3 in the arrangement | positioning of the said embodiment or the arrow C position, even if any of the intake passage 11p and the heating intake passage 20p is selected by the switching valve 11v, the intake air is taken forward Can be sent in or sucked in from the rear. On the other hand, arranging the throttle at the position (see arrow B position in FIG. 1) between the branch portion 11b and the connecting portion (downstream end 30b) in the intake passage 11p is the heating intake passage 20p. When is selected, since adjustment of the intake amount becomes difficult, it is not preferable.

Moreover, in the said embodiment, although the internal EGR is used to expand the operation area | region which premixed compression ignition combustion is possible mainly to the low load side, and the supercharger 11t is used to spread it to the high load side, these structures are not necessarily essential. . When the internal EGR or the supercharger is not used, the operating range in which premixed compression ignition combustion is possible is narrowed. However, by applying the present invention, it is possible to use intake air heating and external EGR. In addition, instead of using an internal EGR as a means for widening the operating region in which premixed compression ignition combustion is possible, it is also proposed to increase the compression ratio in the combustion chamber, and the present invention can be applied to such a premixed compression ignition engine. .

In addition, in the said embodiment, although the internal combustion engine which uses gaseous fuel is assumed as a premise, it does not specifically limit but may apply to other types of internal combustion engines, such as a gasoline engine. For example, in the case of a gasoline engine, a fuel supply means may be suitably changed, such as using a carbulator or an injector instead of the mixer in the said embodiment as a fuel supply means.

In addition, in the said embodiment, although the circulating cooling water of an engine is used as a heat exchange medium of the heat exchanger 40, a heat exchange medium is not specifically limited to this. For example, when the gas engine of the said embodiment is used for a gas heat pump use, you may use the hot water piping for heating which exists in an apparatus. If there is a heat exchange medium that is higher than the low ambient temperature and lower than the EGR gas (exhaust gas), it can be used without particular limitation.

In addition, in the said embodiment, although the supercharger 11t is used in order to enlarge the operation area | region which can premix compression ignition combustion, this is not essential. When the necessity of widening the operating region where premixed compression ignition combustion is possible to the high load side is low, the control by the supercharger and the external EGR may be omitted. The case where the need to widen the driving region to the high load side is low corresponds to a case where a commercial driving region is used for a narrowly restricted low load station, such as some stationary engines. In addition, although not as the case of using the supercharger, when the external EGR is used in combination with the high load side of the control by the internal EGR, that is, the internal EGR decreases and the amount of the mixed suction is increased, as shown in e of FIG. 6, the supercharger is not used. The operable area of premixed compression ignition combustion can be enlarged without. In Fig. 6, a, b, and e are regions for controlling the amount of internal EGR, a is a region in which intake heating is performed under low ambient temperature and low load to suppress misfire, and e is an external EGR under high load. By using it together, knocking is suppressed and the area | region which expands an operation area is shown.

1 is an overall schematic diagram of a premixed compression ignition engine and an intake and exhaust device according to one embodiment of the present invention;

FIG. 2 is a chart showing a control state of an EGR valve and a switching valve of the premixed compression ignition engine of FIG. 1,

3 is a schematic view showing an operating region when the premixed compression ignition engine of FIG. 1 is used,

4 is an overall schematic view showing a first modification of the premixed compression ignition engine in FIG. 1,

5 is an overall schematic view showing a second modification of the premixed compression ignition engine of FIG. 1,

FIG. 6 is a schematic diagram showing an operating region in the case where the operating region in which the premixed compression ignition combustion is possible without using a supercharger is enlarged in the premixed compression ignition engine of FIG. 1.

Claims (6)

Combustion chamber, An intake passage that serves as an intake passage for the combustion chamber, An exhaust passage serving as an exhaust passage from the combustion chamber, An EGR passage communicating with the exhaust passage and the intake passage, for returning a part of the exhaust gas from the combustion chamber to the combustion chamber as an EGR gas; A heat exchanger formed in the middle of the EGR passage and cooling the EGR gas, An EGR valve formed in the middle of the EGR passage, for adjusting the opening and closing state of the EGR passage, A heating intake passage branched from a branch portion formed upstream from a downstream end of the EGR passage in the intake passage, and further downstream connected to an upstream side of the heat exchanger in the EGR passage; A switching valve for adjusting an amount of intake air passing through each of the intake passage and the heating intake passage on the downstream side from the branch; When the EGR valve is closed, the intake air flowing into the combustion chamber is switched so as to pass through at least one of the intake passage and the heating intake passage on the downstream side of the branch portion, Control means for controlling the intake air flowing into the combustion chamber to switch the switching valve so as to pass only the intake passage downstream of the branch when the EGR valve is open; Premixed compression ignition engine, characterized in that having a. The method of claim 1, The EGR valve is a premixed compression ignition engine, characterized in that the EGR passage is formed upstream from a downstream end of the heating intake passage. The method according to claim 1 or 2, The switching valve is formed in the branch portion pre-mix compression ignition engine, characterized in that. The method according to claim 1 or 2, The switching valve and the EGR valve are formed in a communication portion of the heating intake passage and the EGR passage. The method according to any one of claims 1 to 4, The heat exchanger is a pre-mix compression ignition engine that is passed through the circulation cooling water of the engine. In the intake and exhaust device of a premixed compression ignition engine used for a premixed compression ignition engine having a combustion chamber and an exhaust passage serving as an exhaust passage from the combustion chamber, An intake passage leading to the combustion chamber; An EGR passage communicating with the exhaust passage and the intake passage, for returning the exhaust gas from the combustion chamber to the combustion chamber as an EGR gas; A heat exchanger formed during the EGR passage and cooling the EGR gas, An EGR valve formed in the middle of the EGR passage, for opening and closing the EGR passage, A heating intake passage branched from a branch portion formed upstream from a downstream end of the EGR passage in the intake passage, and further downstream connected to an upstream side of the heat exchanger in the EGR passage; A switching valve for adjusting an amount of intake air passing through each of the intake passage and the heating intake passage on a downstream side from the branch; When the EGR valve is closed, the intake air flowing into the combustion chamber is switched so as to pass through at least one of the intake passage and the heating intake passage on the downstream side of the branch portion, Control means for controlling the intake air flowing into the combustion chamber to switch the switching valve so as to pass only the intake passage downstream of the branch when the EGR valve is open; An intake and exhaust device of a premixed compression ignition engine, characterized in that it has a.

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